Key Engineering Materials Vol. 875

Abstract: The development of metal-matrix composites (MMCs) has mainly been driven by the growing needs of modern applications for lightweight materials yet strong enough to withstand high service loading. On the other hand, carbon nanotubes (CNTs) presenting excellent combination of mechanical and physical properties have already performed as an excellent strengthening to reinforce MMCs. In present study, an air induction furnace was used to fabricate aluminum-multiwall carbon nanotubes (Al-MWCNTs) composite. The process was benefited for better dispersion of the CNTs, which was validated during microscopic studies. Additionally, the mechanical properties were significantly augmented i.e., the yield strength from 64±3 to 115±2 MPa, the tensile strength from 82±2 to 125±3 MPa for matrix material and Al-CNTs composite, respectively. The structural analysis including, grain size, crystallite strain and dislocation density were investigated using X-ray diffraction to relate with the improvement in the properties.

Abstract: In this study, an industrial method is provided for the synthesis of zinc oxide (ZnO) nanoparticles by a simple and economical wet chemical precipitation reaction between Zinc Chloride (ZnCl2) and Sodium Hydroxide (NaOH) at low temperatures less than 80 °C. In first step, Small quantity of ZnO powder is produced in laboratory scale. As-synthesized lab-scale ZnO powders were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Orthogonal experiments were performed to find out the optimal conditions for the maximum yield of ZnO powder. In second step, the process flow diagram (PFD), material & energy balance and design of reactor were done on the basis of lab-scale data. Overall, this research work proposes that ZnO powder can be manufactured easy and economical method which can be used for various branches of industry: rubber, pharmaceutical, cosmetics, textile, electronic etc.

Abstract: Thermally reduced graphene oxide (trGO) was successfully prepared and confirmed by XRD then dispersed in polystyrene (PS) and Acrylonitrile-Butadiene-Styrene (ABS) polymers and evaluated for EMI shielding in microwave and infrared (IR) region. Thickness of prepared polymer/trGO composite films were 200-250 micron. It was observed that trGO has more compatibility with PS then ABS and dispersed more easily and uniformly in PS than ABS. This effect was also observed in IR shielding as ABS+15trGO have 3% transmission and PS+1% trGO have 1.5% transmission. Maximum 29 dB and 25 dB shielding effectiveness was measured by vector network analyzer (VNA) in microwave region (9-18 GHz) of PS+2% trGO and ABS+2% trGo composite respectively. These results clearly indicating that trGO is more compatible with PS than ABS and form more stable and mature interconnected network structure in PS at lower concentrations.

Abstract: Polymer nano composites based on poly vinyl chloride matrix were fabricated using polyaniline (PANI) and graphene nano platelets (GNP) as electrically conductive nano filler for the application of electromagnetic interference (EMI) shielding. DC conductivity was first evaluated by using cyclic voltammetry and found an increasing trend of electrical conductivity as PANI and GNP was added in PVC matrix that confirms the formation of electrically conductive network structure. Dielectric properties like dielectric constant, dielectric loss and AC conductivity were evaluated in frequency range of 100 Hz to 3 MHz that gives basic prediction for EMI shielding effectiveness. Vector Network Analyzer (VNA) was used to assess EMI shielding properties using coaxial cable method in 11GHz to 20GHz range and it was found that a maximum of 29 dB shielding was archived with the incorporation of 15 wt% of PANI in PVC. This value increased to 56 dB as 5 wt% GNP added in PVC/PANI 15 wt% blend. Interaction of matrix with filler, nature of filler and dispersion of filler in matrix are the key parameters for achieving high shielding effectiveness.

Abstract: Nanofluid is well known as smart fluid which has high ability to recover oil. Therefore, it gains more significant effect in oil and gas industry. With the low concentration of nanofiller in nanofluid is used to enhance the numerous characteristics for oil recovery applications. Then, the main feature is the size of reinforcing agent and properties along matrix medium. Nano dimensional particles suspension in polymeric matrix have major advantages are stable sedimentation, optical, mechanical, electrical, and rheological properties that can be affected during the synthesis of nanofluids. Therefore nanoparticles/polymeric nanofluid have exceptional characteristics over the conventional fluid. Mixed nanoparticles/polymeric nanofluid in the presence of surfactant have effective interfacial tension and wettability which is evident for the development of nanofluids for oil recovery. In this context, the designed experimental study of silica/PVP nanofluids is synthesized via two step methods and characterized by SEM, TG/DTA, contact angle measurement, centrifugal effect and sedimentation test intended for Enhanced Oil Recovery (EOR) system.

Abstract: This work explores the potential of adsorption of Pb2+ by hydrothermally synthesized alumina. In comparison to other heavy ion removal techniques, adsorption is preferred in the current study as it has the edge of ease of operation and environment friendly characteristics. Synthesis of high surface area alumina whiskers was achieved by hydrothermal route which were subsequently employed for the active adsorption of lead ions. AACH (Ammonium Aluminum Carbonate Hydroxide), used as precursor for alumina, was calcined at three different temperatures i.e. 700, 900 and 1100 °C to form alumina whiskers. These whiskers were characterized by XRD, SEM, BET and FTIR. Various adsorption parameters such as contact time, pH, initial metal concentration were studied for lead ions. Maximal removal efficiency was obtained for the specimen having pH 4 and calcined at 700 °C for 60 minutes. Kinetic data was best described by pseudo second order model, whereas the adsorption equilibrium data obeyed the Langmuir adsorption isotherm model.

Abstract: The most widely used personal protective system against heat stress is cooling vest that contains phase change material (PCM) for thermal energy storage. PCMs have the property of absorbing/releasing heat when they change their phase at their melting point. If the PCM has greater heat of fusion, more heat is absorbed; furthermore, good thermal conductivity assists in efficient removal of heat. In this work different PCMs are explored for use in personalized cooling vest. Hexadecane is finally selected to be used as a PCM having a melting point of 18-20 °C (which lies in the human thermal comfort) and heat of fusion of 241 kJ/kg. Carbon nanotubes have excellent capability of increasing thermal conductivity of a material. Carbon nanotubes were added in hexadecane, and latent heat of fusion of the mixture increased up to 262.6 kJ/kg.

Abstract: A highly active Platinum Group Metal (PGM) and non-PGM electrocatalysts with thermally extruded nanotubes have been prepared for Proton Exchange Membrane (PEM) fuel cell by sintering Nickel zeolitic imidazole framework (Ni-ZIF). Preeminent electro-catalytic activities have been observed through single fuel cell tests and rotating disk electrode (RDE). This study involves the comparison of Oxygen Reduction Reaction (ORR) activities and fuel cell (FC) test station performance of two catalyst Nickel and Platinum mixed Nickel nanotubes (Ni NT, Ni/Pt NT) respectively. The acidic cells with corresponding Ni and Ni/Pt catalysts delivers peak power densities of 325 mWcm^-2 and 455 mWcm^-2 at 75 °C inside fuel cell. Our results indicate that, the synthesized Nickel nanotubes has profound effect on catalytic performance of both PGM and non-PGM electro catalysts.

Abstract: In this study, mechanical properties of friction stir welded Aluminum Alloy (AA) 6061 in three different heat treatment conditions i.e. Annealed (O), Artificially aged (T6) and Post Weld Heat Treated (PWHT) were compared. Plates were welded in a butt joint form. Parameters were optimized and joints were fabricated using tool rotational speed and travel speed of 500 rpm and 350 mm/min respectively. Two sets of plates were welded in O condition and out of which one was, later, subjected to post weld artificial aging treatment. Third set was welded in T6 condition. The welds were characterized by macro and microstructure analysis, microhardness measurement and mechanical testing. SEM fractography of the tensile fracture surfaces was also performed. Comparatively better mechanical properties were achieved in the plate with PWHT condition.

Abstract: The most popular aluminium alloy used for the automotive applications is the wrought-Al alloy, where its popularity arises from its intrinsic characteristics such as, excellent formability, crash resistance, corrosion resistance and excellent specific strength. In the coming decades the use of aluminium alloys is expected to increase within automotive and aerospace industries, where this will source for an upsurge in Al recycling. Problems arise during Al recycling, where there is a steady build-up of Fe content, as this is recognised as being an impurity element. Fe has very little solubility in Al in its solid state and precipitation of these Fe intermetallics (IMC), in the Al matrix decrease mechanical properties, due to the Fe IMC brittle nature. These Fe-rich IMC also have very little cohesion to the Al matrix and can separate from the Al matrix resulting in the development of voids, where the initiation of microcracks becomes ostensible when subjected to thermomechanical processing. In order to curtail the damaging effect of the Fe IMC it so of importance to alter the nucleation and growth characteristic of the Fe rich IMC during solidification. Addition of trace elements and the manipulation of cooling rates have shown to be an effective technique to alter the Fe IMC morphology. In order observe the morphological evolution of the Fe IMC, various experiments were conducted using Al-1Si-1Mg-1Fe alloy with the addition of Mn and TiB₂-based commercial grain refiner. Microstructural analysis of the primary α-Al and Fe IMC are observed and the morphological evolution of the Fe IMC is analysed with respects to the addition of Mn and TiB₂. How the addition of these trace elements influence the growth characteristics and chemistry of the Al melt is also presented in this work.